This invention relates to an actuation apparatus for a control switch which, in accordance with the position of a switching member, produces various control signals, in which an actuation arm coupled with the switching member is provided. The present invention relates more particularly to such an actuation device provided with an actuation arm which is pivotable out of a central position of rest about a pivoting shaft counter to the restoring force of a torsion spring provided with off-standing free arms, in which one stationary initial stop is provided for each free arm for the position of these in a position of rest and in which at least one coupler in contact with the free arms is connected with the actuation arm.
Actuation apparatuses of the above-mentioned type are particularly used in closed-looped and open-looped drives for sewing machines and the like, such as are known from the periodical Bekleidung und Wasche, No. 7, 1970, pages 446-470. Close-looped and opened-looped drives of this type are also known from the German Federal Republic Design Application 75 39 310, corresponding to U.S. Pat. No. 4,100,868. The actuation apparatus in this known apparatus is actuated via a pedal which can be actuated by the seamstress with her foot. The transmission of motion from the pedal to the actuation apparatus is effected via a rod linkage. When the switching member of the control switch moves in one direction out of the position of rest, various rotary speeds of the drive, which increase with the degree of deflection out of the position of rest, are triggered, while if the actuation arm pivots out of the position of rest in the opposite direction, for instance, other functions are triggered such as the actuation of a thread cutter or the like.
Control switches of this kind are known; switching can take place in discrete steps or in an ungraduated fashion as well. These switches can furthermore function using contact banks or may be embodied without contacts.
In a known actuation apparatus such as the apparatus described in the first paragraph of the present application, the free arms of the torsion spring are bent towards one another and lie in contact with a stationary stop disposed between them. A coupler coupled with the actuation arm is further disposed between them, which defines the position of the actuation arm. Upon the movement of the actuation arm in one or the other direction, one free arm of the other is deflected, generating a corresponding restoring force. A limitation of the switch travel is obtained in that the coupler is simultaneously guided in a stationary oblong slot of a housing, the ends of which represent the end stops for the coupler. A so-called pressure point i.e. a perceptable increase in the necessary adjustment force before the beginning of the actual switching procedures is effected by an extensive, spring-loaded lever linkage which is connected via cam connections with the actuation arm.